1. Field of the Invention
The present invention relates to keyless entry systems for motor vehicles and more particularly to a keyless entry system for trucks which is operable during certain periods when the vehicle is left running.
2. Description of the Prior Art
Keyless entry systems to motor vehicles have become a common and popular feature on automobiles. Truck manufacturers have followed the lead of automobile manufacturers and added automotive type keyless entry systems to trucks. However, keyless entry systems have features adapted for common automotive operation which are less appropriate for trucks. Chief among these features is that automotive keyless entry systems are designed to be inoperable if the motor vehicle Ignition switch is in the run position. The door lock modules of the prior art have an enable input connected to a signal source indicative of the position of the ignition switch. If the ignition switch is in the run position the door lock module is defeated. An intention here is that car drivers not be encouraged to leave their cars running while locked and unattended. Leaving a gasoline engine running unattended is also highly inefficient. It is, also undesirable that the keyless entry system be operational when a vehicle is in motion.
Trucks, unlike automobiles, typically use diesel engines, and truck drivers commonly leave such engines running with the vehicle unattended for short breaks at rest areas. Given the occasional difficulty of restarting diesel engines, particularly in cold weather, and the low fuel consumption of diesels at idle, it is much more reasonable to leave a diesel running during a break than a gasoline fired internal combustion engine. Truck drivers have good reason to be able to use a keyless entry system to lock and unlock their rigs while the vehicle is left running, but the vehicle is parked. It would be advantageous to truck manufacturers to be able to continue to use automotive keyless systems with a minimum of modifications to order to continue to enjoy the low cost such systems have due to the large manufacturing runs provided by the automobile industry.
While it is possible to simply disconnect the door locking mechanisms of a keyless entry system from the ignition switch, such an action undesirable consequences. The keyless entry system would be active when the vehicle was in motion. Interior dome light mechanisms would remain on a sixty-second dimming cycle. This could have the result that the vehicle could be in motion with the dome light on.
The invention provides a keyless entry system for a motor vehicle which is operable when the vehicle""s engine is running and the vehicle""s park brake is set. The keyless entry system includes an ignition position signal source and a door lock module having an enable input connected to be responsive to an output from the ignition position signal source. The ignition position feed signal is connected to the door lock module enable through a park brake lamp. As a result the enable input to the door lock module is then connected in common with one terminal each of the a park brake lamp switch and the park brake lamp. When the park brake lamp switch is closed by setting the park brake, the ignition switch position signal on the enable input is sunk by the park brake switch and the potential level on the enable input is reduced, enabling the door lock module to operate as though the ignition switch had been moved to off. Operation of the door lock module is otherwise unaffected.
Additional effects, features and advantages will be apparent in the written description that follows.